Ink formulations and film constructions thereof

Abstract

Ink formulations suitable for deposition upon the intermediate transfer member of an indirect printing system and for transfer therefrom to a substrate. The inks are aqueous inkjet inks comprising an organic polymeric resin and a colorant. Ink film constructions including a plurality of continuous ink films fixedly adhered to the printing substrate that can be obtained with these inks are also disclosed. The inks and the printed constructions are such that the ink films and the dried inks composing them have a first dynamic viscosity within a range of 106 cP to 5·107 cP at at least a first temperature within a first range of 60° C. to 87.5° C., and a second dynamic viscosity of at least 6·107 cP, for at least a second temperature within a second range of 50° C. to 55° C.

What is claimed is: 
     
       1. A water-based ink formulation comprising:
 (a) a solvent containing water; 
 (b) at least one colorant dispersed or at least partly dissolved within the solvent; and 
 (c) at least one organic polymeric resin, dispersed within the solvent; and 
 (d) a softening agent selected to reduce a glass transition temperature (T g ) of said polymeric resin, the ink formulation forming, when dried, a substantially dry ink residue having: 
 
       (i) a first dynamic viscosity within a range of 10 6  cP to 3·10 8  cP over at least part of a first temperature range of 60° C. to 110° C.; and 
       (ii) a second dynamic viscosity of at least 6·10 7  cP, over at least a part of a second temperature range of 50° C. to 55° C.; 
       said second dynamic viscosity at 55° C. exceeding the first dynamic viscosity at 85° C.; 
       said softening agent having a pure vapor pressure of at most 0.40 kPa at 150° C.; 
       at least one particular resin of said organic polymeric resin having an elevated glass transition temperature (T g ) of at least 56° C.; 
       wherein said softening agent is selected and/or added in an amount to reduce said elevated glass transition temperature by at least 5° C.; 
       wherein the ink formulation is devoid of inorganic filler particles; 
       and wherein a weight ratio of said organic polymeric resin to said colorant is at least 3.5:1. 
     
     
       2. The ink formulation of  claim 1 , wherein the formulation is an aqueous inkjet ink having at least one of:
 (i) a viscosity of 2 to 25 cP at at least one particular temperature in a jetting temperature range of 20-60° C.; and 
 (ii) a surface tension of at most 50 milliNewton/m at at least one particular temperature within said jetting temperature range. 
 
     
     
       3. A water-based aqueous inkjet ink formulation comprising:
 (a) a solvent containing water; 
 (b) at least one colorant dispersed or at least partly dissolved within the solvent; and 
 (c) at least one organic polymeric resin, dispersed within the solvent; and 
 (d) a softening agent selected to reduce a glass transition temperature (T g ) of said polymeric resin, the ink formulation forming, when dried, a substantially dry ink residue having: 
 
       (i) a first dynamic viscosity within a range of 10 6  cP to 3·10 8  cP over at least part of a first temperature range of 60° C. to 110° C.; and 
       (ii) a second dynamic viscosity of at least 6·10 7  cP, over at least a part of a second temperature range of 50° C. to 55° C.; 
       said second dynamic viscosity at 55° C. exceeding the first dynamic viscosity at 85° C.; 
       said softening agent having a pure vapor pressure of at most 0.40 kPa at 150° C.; 
       at least one particular resin of said organic polymeric resin having an elevated glass transition temperature (T g ) of at least 54° C.; 
       wherein said softening agent is selected and/or added in an amount to reduce said elevated glass transition temperature by at least 5° C.; 
       wherein the ink formation is devoid of inorganic filler particles: 
       and wherein the ink formulation has at least one of the following properties:
 (i) a viscosity of 2 to 25 cP at at least one particular temperature in a jetting temperature range of 20-60° C.; and 
 (ii) a surface tension of at most 50 milliNewton/m at at least one particular temperature within said jetting temperature range. 
 
     
     
       4. The formulation of  claim 3 , wherein said softening agent is selected and/or added in an amount to reduce said elevated glass transition temperature by at least 7° C. 
     
     
       5. The formulation of  claim 3 , wherein said softening agent is selected and/or added in an amount to reduce said elevated glass transition temperature by at least 10° C. 
     
     
       6. The formulation of  claim 3 , wherein said softening agent is selected and/or added in an amount to reduce said elevated glass transition temperature by at least 15° C. 
     
     
       7. The ink formulation of  claim 3 , the formulation having a total solids content, and wherein a weight ratio of said softening agent to said total solids content is at least 0.08. 
     
     
       8. The ink formulation of  claim 3 , the formulation having a total solids content, and wherein a weight ratio of said softening agent to said total solids content is at least 0.10. 
     
     
       9. The formulation of  claim 3 , wherein ΔT defines a temperature differential between a temperature (T F ) at which said dried ink residue begins to exhibit a particular degree of flowability, and a baseline temperature (T B ):
   Δ T=T   F   −T   B  
 
 said degree of flowability being defined by a critical viscosity (μ CR ) at which said degree of flowability is achieved, 
 and wherein, when said baseline temperature equals 50° C., and said critical viscosity equals 10 8  cP, said temperature differential is at least 3° C. 
 
     
     
       10. The formulation of  claim 3 , said polymeric resin including, mainly including, or consisting essentially of an acrylic-based polymer selected from the group consisting of an acrylic polymer and an acrylic-styrene copolymer. 
     
     
       11. The ink formulation of  claim 3 , wherein a weight ratio of said organic polymeric resin to said colorant is at least 3.5:1. 
     
     
       12. The formulation of  claim 11 , wherein said weight ratio of said organic polymeric resin to said colorant is at least 4:1. 
     
     
       13. The formulation of  claim 11  wherein said weight ratio of said organic polymeric resin to said colorant is at least 5:1. 
     
     
       14. The formulation of  claim 13 , wherein said elevated glass transition temperature (T g ) is at least 60° C. 
     
     
       15. The formulation of  claim 14 , wherein a weight ratio of said softening agent to said substantially dry ink residue is within a range of 0.06 to 0.25. 
     
     
       16. The ink formulation of  claim 13 , the formulation having a total solids content, and wherein a weight ratio of said softening agent to said total solids content is at least 0.08. 
     
     
       17. The formulation of  claim 11 , wherein said elevated glass transition temperature (T g ) is at least 60° C. 
     
     
       18. An ink film construction including: (a) a printing substrate; and (b) at least one substantially dry ink film, fixedly adhered to a surface of the printing substrate, the ink film containing at least one colorant dispersed in an organic polymeric resin; wherein a dynamic viscosity of the ink film is within a range of 10 6  cP to 5·10 7  cP over at least part of a first temperature range of 60° C. to 87.5° C., and at least 6·10 7  cP over at least a part of a second temperature range of 50° C. to 55° C., wherein a weight ratio of said organic polymeric resin to said colorant is at least 3.5:1 and wherein the substantially dry ink film is devoid of inorganic filler particles. 
     
     
       19. The ink film construction of  claim 18 , a viscosity of said substantially dry ink residue monotonically increasing with temperature decreasing from 85° C. to 55° C.